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use std::fmt;
use std::error::Error;
use std::sync::mpsc::{channel, Sender, Receiver, RecvError};
#[derive(Debug)]
pub enum FunnelError {
RecvError(RecvError),
NoSourcesError,
}
impl fmt::Display for FunnelError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
FunnelError::RecvError(ref contained) => contained.fmt(f),
FunnelError::NoSourcesError => write!(f, "Funnel has no input sources."),
}
}
}
impl Error for FunnelError {
fn description(&self) -> &str {
match *self {
FunnelError::RecvError(ref contained) => contained.description(),
FunnelError::NoSourcesError => "Cannot read from a funnel before adding receivers.",
}
}
fn cause(&self) -> Option<&Error> {
match *self {
FunnelError::RecvError(ref contained) => Some(contained),
FunnelError::NoSourcesError => None,
}
}
}
#[derive(Debug)]
pub struct Funnel<T> {
sources: Vec<Receiver<T>>,
next_index: usize
}
impl<T> Funnel<T> {
pub fn new() -> Funnel<T> {
Funnel {
sources: Vec::new(),
next_index: 0
}
}
pub fn push(&mut self, receiver: Receiver<T>) {
self.sources.push(receiver);
}
pub fn len(&self) -> usize {
self.sources.len()
}
pub fn remove(&mut self, index: usize) -> Receiver<T> {
self.sources.remove(index)
}
pub fn add_receiver(&mut self) -> Sender<T> {
let (tx, rx) = channel();
self.push(rx);
tx
}
pub fn recv(&mut self) -> (Option<T>, Vec<(FunnelError, usize)>) {
let mut errors: Vec<(FunnelError, usize)> = Vec::new();
let mut index: usize = self.next_index;
if self.sources.len() == 0 {
errors.push((FunnelError::NoSourcesError, 0));
return (None, errors);
}
loop {
match self.sources[index].recv() {
Err(e) => errors.push((FunnelError::RecvError(e), index)),
Ok(value) => {
self.next_index = (index + 1) % self.sources.len();
return (Some(value), errors);
},
};
index = (index + 1) % self.sources.len();
if index == self.next_index {
break;
}
}
(None, errors)
}
}
#[cfg(test)]
mod tests {
use super::Funnel;
use std::sync::mpsc::channel;
#[test]
fn single_read() {
let mut funnel = Funnel::new();
let (tx, rx) = channel();
funnel.push(rx);
let _ = tx.send(1).unwrap();
let (received, errors) = funnel.recv();
assert!(received.is_some());
assert!(match received {
Some(value) => value == 1,
_ => false,
});
assert_eq!(errors.len(), 0);
}
#[test]
fn multiple_read() {
let mut funnel: Funnel<i32> = Funnel::new();
let writer1 = funnel.add_receiver();
let writer2 = funnel.add_receiver();
let _ = writer1.send(1).unwrap();
let _ = writer2.send(2).unwrap();
let (received, errors) = funnel.recv();
assert!(received.is_some());
println!("{:?}", received);
assert!(match received {
Some(value) => value == 1,
_ => false,
});
assert_eq!(errors.len(), 0);
let (received, errors) = funnel.recv();
assert!(received.is_some());
println!("{:?}", errors);
assert!(match received {
Some(value) => value == 2,
_ => false,
});
assert_eq!(errors.len(), 0);
}
}